1. Field of the Invention
The present invention is concerned with improved blade-type, air dielectric switchgear apparatus used by electrical utilities in their transmission and distribution systems. More particularly, it is concerned with such switchgear having a novel mounting arrangement for the switchblades therein, and with removable and field-replaceable bushing assemblies associated with the respective internal switch mechanisms of the gear.
2. Description of the Prior Art
Electrical utilities make use of a large number and variety of switchgear devices in their transmission and distribution systems. Such devices are used for sectonalizing purposes in order to isolate respective zones for component repair or the like and to provide desirable system coordination. System switchgear of this type may be of the pad-mounted variety and can include vacuum switches under oil or air dielectric switchgear.
Air dielectric switchgear are typically larger than the vacuum variety, and usually include internal switchblade arrangements, i.e., they are provided with a stationary contact and a movable contact, the latter being a part of an elongated, pivotally supported switchblade. Furthermore, such switchgear typically have appropriate source and load side bushings extending through opposed sidewalls of the switchgear housing. Conventional elbow-type line connectors are then secured to the respective bushings, as those skilled in the art will readily understand.
In the latter connection, it commonly occurs in the servicing and maintenance of switchgear that the bushings originally provided become damaged. In particular, and especially in the case of high amperage source side bushings, it is the common practice to install a connector elbow over the bushing and to insert a relatively long bolt through the elbow and into threaded engagement with the bushing structure. Inasmuch as attachment and detachment of such elbow may often occur under live conditions, use must be made of elongated hotline tools. As a consequence, it is relatively easy for a lineman to cross-thread or strip the threading of the bushing. This in turn necessitates that the bushing be replaced.
A prime drawback of many conventional switchgear devices is that bushing replacement cannot be readily completed in the field. Indeed, in certain types of gear, bushing replacement can be so formidable as to require that the apparatus be moved from service and taken to a repair shop. Obviously, this is an expensive and time-consuming operation.
In short, there is a real and unsatisfied need in the art for switchgear apparatus equipped with field-replaceable bushing assemblies which can be readily and easily changed by lineman in the field without special tools or an undue amount of labor.